[content shell] remove spurious printf format

content/shell/webkit_test_runner_host.cc

Index: content/shell/webkit_test_runner_host.cc
diff --git a/content/shell/webkit_test_runner_host.cc b/content/shell/webkit_test_runner_host.cc
index 88b2f124d25f9db4820d714bcc46c8ce7398d512..03ca79e013da3ad17a0a965e3dd93bfb91a20646 100644
--- a/content/shell/webkit_test_runner_host.cc
+++ b/content/shell/webkit_test_runner_host.cc
@@ -67,9 +67,9 @@ void WebKitTestResultPrinter::PrintImageHeader(
     const std::string& expected_hash) {
   if (state_ != IN_IMAGE_BLOCK || capture_text_only_)
     return;
-  *output_ << "\nActualHash: " << actual_hash << "%s\n";
+  *output_ << "\nActualHash: " << actual_hash << "\n";
   if (!expected_hash.empty())
-    *output_ << "\nExpectedHash: " << expected_hash << "%s\n";
+    *output_ << "\nExpectedHash: " << expected_hash << "\n";
 }
 
 void WebKitTestResultPrinter::PrintImageBlock(